I've had a number of potential clients, even the ones who just first contacted my company, ask us this question. We were offered shares in the future company, free advertising, partnerships, profit sharing - just to name a few of the ‘benefits’ we were offered.
’Opportunities’ like this one are a trap. The owner of the business cannot afford to hire a web developer or pay for custom software development. If he could, he would not ask a freelancer who builds his website to become his business partner. The other person only wants you for your hard work.
Other than that, you’re a professional. You already have a business. You’re either a freelancer or a small team or a web studio or a web agency. If you accept to work on your client’s business, your own will suffer. You’ll have to give one business up. Are you ready to give up your business right now and let a stranger have a say in your destiny?
Treat every business partnership like a marriage. Would you marry a person without dating her for a longer period of time? Would you welcome every person who earns a salary of $10,000 a month into your home and into your life?
Say ‘no, thank you, I already have a business’ and move on.